Polyethylene polymers, their blends and articles made therefrom are generally known in the art. Such polymers have typically been made from ethylene and a C3-C6 α-olefin comonomer with a variety of catalysts systems using Ziegler-Natta catalysts, chrome catalysts, metallocene catalysts, constrained-geometry catalysts, etc. in a variety of platforms including gas-phase processes, solution processes, high pressure tubular processes, slurry processes, etc.
U.S. Pat. No. 6,255,426 describes polymers of ethylene and at least one α-olefin having at least five carbon atoms obtained by a continuous gas phase polymerization process using supported catalyst of an activated molecularly discreet catalyst such as a metallocene. The polymerization process is performed in the substantial absence of an aluminum alkyl-based scavenger, and results in a linear low density polyethylene having a combination of good shear thinning behavior and impact strength.
WO 2004/022646 A1 describes heat shrinkable monolayer and multilayer films having good optical and mechanical properties. The films are formed of a blend of a polyethylene copolymer and a second polymer, such as a low density polyethylene. In particular, monolayer and multilayer shrink films are described that include in at least one layer a metallocene-catalyzed polyethylene resin. Also described are articles wrapped with such films.
WO 2004/022634 A1 describes stretch films having at least one layer formed of or including a polyethylene copolymer having a draw ratio of at least 250%, a tensile stress at the natural draw ratio of at least 22 MPa, and a tensile stress at second yield of at least 12 MPa.
U.S. Pat. No. 7,951,873 discloses, among other things, an ethylene copolymer having: i. a composition distribution breadth index of at least 70%; ii. a melt index I2.16 of from about 0.3 to about 2.0 g/10 min; iii. a molecular weight distribution of from about 2.5 to about 5.5; iv. a density of from about 0.915 to about 0.940 g/cm3; and v. a melt index ratio, I21.6/I2.16, of from about 25 to about 50.
Of all these polyethylene polymers, a special family of polymers has distinguished itself for its performance and versatility known as ENABLE™ mPE available from ExxonMobil Chemical Company, Houston, Tex. ENABLE™ mPE offers an unprecedented combination of polymer film processing advantages and higher alpha olefin (HAO) performance. A good balance of operational stability, extended output, versatility with HAO performance, and resin sourcing simplicity are among the unique properties of this family of polyethylene polymers. For example, Ser. No. 62/082,896, filed Nov. 21, 2014, discloses ENABLE™ 1602 metallocene polyethylene resin having a melt index (I2.16) of 0.2 g/10 min and a density of 0.916 g/cm3 incorporated in a multi-layer film. (See the Examples). Commercial ENABLE™ mPE are available at densities from 0.920-0.935 g/cm3 and melt indexes (I2.16) from 0.3-1.0 g/10 min.
Even though these references describe polymers using many of the same monomers, catalysts, and processes, none provides a polymer that may produce a film having a good balance of two or more of high tensile strength, high dart impact, high puncture resistance, and low seal initiation temperature.